Tungsten-silicide reoxidation process including annealing in pure nitrogen and subsequent oxidation in oxygen

Claim 1

A method of fabricating a complementary metal-oxide semiconductor (CMOS) integrated circuit where a reoxidation layer is formed on an insulated gate member which overlies a substrate and in which said insulated gate member is comprised of an amorphous silicon-rich tungsten silicide layer overlying a polysilicon layer, comprising the following steps in the order named of: (a) forming an oxidation insulating layer using excessive silicon atoms from said silicon-rich tungsten silicide layer over opposite sides and upper surface of said gate member; (b) forming spacers about said gate member; (c) etching said oxidation insulating layer to expose upper surface of said silicide layer of said gate member; (d) forming source and drain regions in said substrate adjacent to said gate member; (e) annealing said gate member after said oxidation insulating layer has been etched from said upper surface of said silicide layer of said gate member in a furnace having substantially pure nitrogen ambient to anneal said silicide layer and freeing silicon atoms from said polysilicon layer; (f) forming said reoxidation layer about said gate member by introducing oxygen into said heating furnace, wherein oxygen atoms react with said silicon atoms to form said reoxidation layer such that said reoxidation layer is substantially planarized and uncontaminated.

Claim 2

A method of fabricating a complementary metal-oxide semiconductor (CMOS) integrated circuit where a reoxidation layer is formed on an insulated gate member which overlies a substrate and in which said insulated gate member is comprised of an amorphous silicon-rich tungsten silicide layer overlying a polysilicon layer, comprising the following steps in the order named of: (a) forming an oxidation insulating layer using excessive silicon atoms from said silicon-rich tungsten silicide layer over opposite sides and upper surface of said gate member; (b) forming spacers about said gate member; (c) etching said oxidation insulating layer to expose upper surface of said silicide layer of said gate member; (d) forming source and drain regions in said substrate adjacent to said gate member; (e) annealing said gate member after said oxidation insulating layer has been etched from said upper surface of said silicide layer of said gate member in a furnace having substantially pure nitrogen ambient to anneal said silicide layer and freeing silicon atoms from said polysilicon layer; (f) forming said reoxidation layer about said gate member by introducing oxygen into said heating furnace, wherein oxygen atoms react with said silicon atoms to form said reoxidation layer such that said reoxidation layer is substantially planarized and uncontaminated.

Claim 7

A method of fabricating a complementary metal-oxide-semiconductor (CMOS) field-effect transistor integrated circuit where a reoxidation layer is formed on an insulated gate member which overlies a substrate and in which said insulated gate member is comprised of a silicon-rich tungsten silicide layer overlying a polysilicon layer, comprising the steps in the sequence that follows of: (a) forming a first silicon oxide insulating layer using excessive silicon atoms supplied from said silicon-rich tungsten silicide layer over opposite sides and upper surface of said gate member; (b) forming a low temperature oxide insulating layer over said first oxide insulating layer; (c) etching said first oxide and said low temperature oxide insulating layers such that said low temperature oxide insulating layer remains adjacent to said first oxide insulating layer which is along opposite sides of said gate member for forming spacers; (d) forming source and drain regions in said substrate adjacent to a portion of said substrate underlying said gate member and its spacers; (e) removing said spacers; (f) annealing said silicide layer of said gate member in a furnace having substantially pure nitrogen ambient after removing said spacers, wherein said annealing step inhibits tungsten atoms from reacting with oxygen atoms during reoxidation and frees silicon atoms from said polysilicon layer; (g) forming said reoxidation layer over said gate member by introducing oxygen into said furnace, wherein oxygen atoms react with said silicon atoms to form said reoxidation layer such that said reoxidation layer is substantially planarized and uncontaminated.

Claim 8

A method of fabricating a complementary metal-oxide-semiconductor (CMOS) field-effect transistor integrated circuit where a reoxidation layer is formed on an insulated gate member which overlies a substrate and in which said insulated gate member is comprised of a silicon-rich tungsten silicide layer overlying a polysilicon layer, comprising the steps in the sequence that follows of: (a) forming a first silicon oxide insulating layer using excessive silicon atoms supplied from said silicon-rich tungsten silicide layer over opposite sides and upper surface of said gate member; (b) forming a low temperature oxide insulating layer over said first oxide insulating layer; (c) etching said first oxide and said low temperature oxide insulating layers such that said low temperature oxide insulating layer remains adjacent to said first oxide insulating layer which is along opposite sides of said gate member for forming spacers; (d) forming source and drain regions in said substrate adjacent to a portion of said substrate underlying said gate member and its spacers; (e) removing said spacers; (f) annealing said silicide layer of said gate member in a furnace having substantially pure nitrogen ambient after removing said spacers, wherein said annealing step inhibits tungsten atoms from reacting with oxygen atoms during reoxidation and frees silicon atoms from said polysilicon layer; (g) forming said reoxidation layer over said gate member by introducing oxygen into said furnace, wherein oxygen atoms react with said silicon atoms to form said reoxidation layer such that said reoxidation layer is substantially planarized and uncontaminated.